The present invention relates to a device for transmitting the position of a control element which can be actuated by the driver of a vehicle.
There is known a device for transmitting the position of a control element which is actuatable by the driver of a vehicle between an idling position and a full-gas position via an electric set-value transmitter which can be displaced by the control element, and via electric transmission means, to a setting member which can be displaced in corresponding manner between an idling position and a full gas position, said member being coupled by coupling means to a actuating member which controls the fuel/air mixture of an internal combustion engine, having at least one mechanical safety transmission element arranged between the control element of the set-value transmitter and the actuating member, by which transmission element the position of the control element can be transmitted to the actuating member.
In such known devices the transmitting of the position of the control element, i.e. customarily the position of the gas pedal, to the throttle valve of a carburetor or the control rod of an injection pump normally takes place electrically via the set-value transmitter coupled to the gas pedal and via electric transmission means which comprise, in addition to wires, an electronic regulator or an electronic control device, to the electric setting member (EP-Al-No. 0123731). The setting member, in its turn, is continuously coupled mechanically in form-locked and force-locked manner to the throttle valve or the control rod which forms the actual actuating member. In order that such an electronically controlled automotive vehicle remain maneuverable even in those rare cases of disturbance in which the position of the set-value transmitter is not transferred correctly to the setting member and the actuating member, at least one mechanical safety transmission element is arranged functionally in parallel with the electric transfer means between the control element of the set-value transmitter or the set-value transmitter itself and the actuating member, in such a manner that upon normal operation of the electric transmission means the safety transmission element is moved along without force by the control element, but in the event of a disturbance in the electric transmission means, it takes over the transmission of the position of the control element to the actuating member. In this way the vehicle automatically is imparted so-called emergency operation capability. In detail, the at least one safety transmission element can consist of an emergency-operation rod or else a Bowden cable. In order that unintentional racing of the engine in the event of a defect be avoided, the actuating member is urged into its idling position by a restoring spring. In order not to act on the safety transmission element upon normal operation of the electric set-value transmitter of the electric transmission means and of the electric setting member, the mechanical safety transmission element can be arranged on the setting member freely movable by a predetermined clearance or play in the direction of displacement, said clearance or play being less than the maximum displacement path. By means of this clearance assurance is also had that if the device is intact the setting member and the actuating member can move unimpeded into a position closer to the idling position than corresponds to the instantaneous set-value transmitter position, for example if the position of the setting member is determined not only by the set-value transmitter position but by additional functions. Such additional functions comprise, for instance, a final speed of rotation limitation or a thrust disconnect. These additional functions are carried out by an electronic regulator. If the safety transmission element has a so-called compensation element which consists essentially of two parts displaceable opposite each other as well as an over-stroke spring, one of the two parts being connected to the setting member and the other to the set-value transmitter or the control element then, particularly in case of a defect in the set-value transmitter but with the electronic regulator still operating, the setting member and the actuating member are moved in the direction towards the idling position although the safety transmission element has already produced a form-locked coupling between the control element and the actuating member after going beyond the clearance. In this device the spring force of the over-stroke spring is greater than that of the return spring. For this reason, by actuation of the control element in the direction of full gas, maneuverable travel operation can take place if one of the electronic elements or parts has failed so that the return spring would move the actuating member into idling position. In this connection the safety transmission element, to be sure, is acted on not only by the force of the return spring but also by frictional and/or adherence forces of the setting member and the coupling means which connect the setting member to the actuating member. When the setting member is blocked, the actuating member can no longer be actuated with the mechanical safety transmission element. Emergency operation is no longer possible. If the setting member is in this situation near the full gas position then, to be sure, by an ordinary known safety system, the feeding of fuel or the ignition can be disconnected in order to avoid danger by uncontrolled operation but in this case the fact is tolerated that the vehicle remains stopped, as a result of which, in unfavorable traffic situations, vehicle and passengers can once again be endangered.
It is an object of the present invention therefore to further increase the safety of a device for the transmission of the position of a control element actuatable by the driver of a vehicle and, in particular, to assure emergency operation capabilities of the vehicle even in case of unfavorable disturbances in connection with which the control member can otherwise not be actuated. At the same time, a release of the mechanical safety transmission element from load is also to take place in these special cases of disturbance. The improved device furthermore is to be characterized by high dependability in operation and the possibility of reliable control of function.